The present invention comprises an optimal and versatile spark ignition system based on an optimally designed voltage doubling, low turns ratio, ultra-high efficiency ignition coil of low output capacitance coupled to a large input capacitor, providing simultaneous high breakdown voltage and high spark current at optimal spark oscillation frequency. The invention is usable in any of simple spark, multi pulse, plasma jet, or multi pulse plama jet modes. Preferably the invention is used in conjunction with simple design, versatile, high efficiency, high pulse rate, multi-pulse capacitive discharge (CD) electronic ignitions, permitting optimization with respect to the spark plasma pulse rate.
A principal purpose of the invention, designated as Pulsed Plasma Ignition, or Pulsed Ignition, is to provide a simply incorporated and retrofitable ignition system which will allow internal combustion (IC) engines to operate under very lean air-fuel ratio mixture conditions for the highest efficiency and lowest exhaust emissions. For the additional case of Diesel engines (Direct Injection (DI) engines) the system will provide effective ignition of the fuel for reduced ignition delay time and more controlled combustion. These advantages are provided by Pulsed Ignition's ability to fire wide gaps and produce high arc current (desired for lean burn engines but heretofore considered impractical).
Current ignition and combustion related equipment are either ineffective or impractical for allowing engines to operate at the 22:1 air-fuel ratio necessary to meet the presently contemplated moderately strict European emission standards. In the U.S. for example, where emission standards have been in force for many years, the rich mixture (14.6:1 air-fuel ratio) three-way catalyst system is exclusively used for gasoline engines.
The conventional Kettering (inductive) ignition system is ineffective in providing ignition of mixtures leaner than about 18:1. Electronic ignition and Capacitive Discharge (CD) ignition are no better as they use the same extremely inefficient ignition coil and provide minimal ignition energy (electrical currents) to the spark. While existing multiple pulse ignition systems, such as U.S. Pat. No. 3,898,971, are superior to these, they suffer from still providing low spark currents and have a low overall efficiency, even when used with the more efficient pulse transformer ignition coil, and provide only slightly better lean mixture ignition properties. They provide substantially the same ignition currents (approximately 100 milliamps) although higher overall energy through multiple pulse sparking. However, the time between pulses is low--too low to be useful at anything but low RPM, and of marginal use in Direct Injection engines where the typical fuel injection time is one to two milliseconds.
In an attempt to substantially increase ignition energy and ignition system efficiency, a class of ignition systems called "plasma jet" was developed, such as U.S. Pat. Nos. 4,122,816 and 4,317,068. These systems were developed under the assumption that standard high voltage ignition coils are inherently inefficient and ineffective for transferring ignition energy to a spark gap, and the energy must be provided by an alternative means. While they provide this alternative means and improved ignition, they are substantially more complex, they require special more complex spark plugs, and suffer from a serious spark plug erosion problem. Furthermore, since they need to fire multiple spark gaps or require expensive high voltage/high current diodes, they are less practical and more difficult to use in lean burn engines, high compression ratio engines, and spark ignited diesel engines.
Other systems fall between these various categories, and fail to address and answer the fundamental questions of providing successful ignition by using the characteristics inherent in ignition coils when specifically coupled to high efficiency high pulse rate multi-pulse capacitive discharge ignition systems--to provide rapid firing wide gap high current plasma jet-like sparks.